Genesis 8:2 - The windows of heaven.

The fountains also of the deep and the windows of heaven were stopped, and the rain from heaven was restrained;
The flood was not only caused by rain for 40 days and 40 nights, it was also caused by the opening of the windows of heaven and the fountains of the deep. I believe the windows of heaven consist of the earth's atmosphere, protecting the earth from meteorites, the sun, so on and so forth. It's possible that a meteorite could have busted the earth's foundation, springing forth the fountains of the deep.

Just as it could have happen then so could it happen in the end as described by Isaiah:
And it shall come to pass, that he who fleeth from the noise of the fear shall fall into the pit; and he that cometh up out of the midst of the pit shall be taken in the snare: for the windows from on high are open, and the foundations of the earth do shake. The earth is utterly broken down, the earth is clean dissolved, the earth is moved exceedingly. The earth shall reel to and fro like a drunkard, and shall be removed like a cottage; and the transgression thereof shall be heavy upon it; and it shall fall, and not rise again. Isaiah 24:18-20


Genesis 8:1 - How the wind blows.

And God remembered Noah, and every living thing, and all the cattle that was with him in the ark: and God made a wind to pass over the earth, and the waters assuaged;
Just as God uses the wind to destroy the wicked (Jeremiah 23:19), he also uses the wind help the righteous. Such was the case when God used the wind to feed the Israelites in the desert (Numbers 11:31).


Genesis 7:24 - Cleansing the earth.

And the waters prevailed upon the earth an hundred and fifty days.
God created the earth and manipulates its elements at will, including the water (Genesis 1:1, 1:6-7, Exodus 14:21, Psalm 24:1). God allowed the water level to rise above the highest montain to cleanse the earth from its wickedness (Genesis 6:1-7). God then gradually returned the waters from whence it came from; at the end of the hundred and fifty days, the water level was back to normal (Genesis 8:3).


Genesis 7:23 - Judgement is inescapable.

And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark.
Just as Noah and his family were delivered during the time of God's wrath, Lot and his family were delivered from the destruction of Sodom and Gomorrah (Genesis 19:12-13). God gives his angels charge to keep the righteous in all their ways because the righteous love and know God (Psalms 91:11-14).

Genesis 7:21 - Take head to the ways of God.

And all flesh died that moved upon the earth, both of fowl, and of cattle, and of beast, and of every creeping thing that creepeth upon the earth, and every man:
Take head to this verse because as it was then so shall it be in the end (Job 22:15-16; Matthew 24:39). The prophet Hosea warned the Hebrews that "every one that dwelleth therein shall languish, with the beasts of the field, and with the fowls of heaven; yea, the fishes of the sea also shall be taken away" (Hosea 4:3) and Zephaniah prophesied that God said "I will consume man and beast; I will consume the fowls of the heaven, and the fishes of the sea, and the stumbling blocks with the wicked: and I will cut off man from off the land, saith the LORD" (Zephaniah 1:3).


Genesis 7:19

And the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered.
Make no mistake, "the high hills" are montains, as noted in Psalms 104:6:
Thou coveredst it with the deep as with a garment: the waters stood above the mountains.


Genesis 7:18 - Refuge in God's Hands

And the waters prevailed, and were increased greatly upon the earth; and the ark went upon the face of the waters.
The ark was the hand of God providing refuge for Noah and his family. The forth edition of the Thompson New Chain-Reference Bible has marked Psalms 104:26 as the parallel passage for this verse.
There go the ships: there is that leviathan, whom thou hast made to play therein.
So, therefore Noah and his family were not only protected from drowning, they also were protected from the horrors that lurked from below, such as leviathan. "Leviathan is often considered to be a demon or natural monster associated with Satan or the Devil, and held by some to be the same monster as Rahab" (Wikipedia.com).


Genesis 7:7 - The day of God's wrath.

And Noah went in, and his sons, and his wife, and his sons' wives with him, into the ark, because of the waters of the flood.
The story of Noah demonstrates the power of faith which not only save him but also his family, as well as the world. Out of faith and fear, Noah built the ark precisely as God had instructed him so that when the flood did come Noah and his family were prepared (Hebrews 11:7; 2 Peter 2:5).

Again, man has been warned about the ending of this world and what must be done to prepare for it. Solomon said that the prudent man will foresee the evil and prepare himself against it; whereas, the simple man will ignore the evil and allow himself to be consumed by it (Proverbs 22:3). Will you be the prudent man that has faith enough to do what is necessary to prepare himself or will you be the simple man that ignore the warning signs and continue living for today? Don't be as those in the days of Noah, that were having the time of their lives, until the flood came (Matthew 24:38; Luke 17:27).


Genesis 6:9 - Divine Fellowship

These are the generations of Noah: Noah was a just man and perfect in his generations, and Noah walked with God.
To walk with God is to fellowship with God as you would with a friend on a walk through the park. However, this walk is not a temporary excursion; but instead, it's a lifelong journey.

Moses walk with God was so personal that "the LORD spake unto Moses face to face, as a man speaketh unto his friend." (Exodus 33:11)


Genesis 6:8 - Salvation is through grace.

But Noah found grace in the eyes of the LORD.
Just as the grace of God saved Noah, the grace of Jesus Christ saves people of today (Acts 15:11; Romans 3:24; Romans 5:15).

Genesis 6:6 - Why should God repent?

And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Some mistake this verse to be in contradiction to Numbers 23:19 which states that God does not repent. However, God has no need to repent because he's never wrong. On the contrary, God repents because of the wrong men do. For example, God repented in making Saul king because of what Saul did (1 Samuel 15:11). God wasn't wrong for making Saul king; Saul was wrong for turning away from God.

Genesis 6:5 - How to manage your imagination.

And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
God wasn't upset that man had a imagination; instead, God was upset with how man used his imagination. As noted from whatgodintended.com the book Becoming Who God Intended, Dr. Eckman teaches how to manage the imagination to please God. The solution is to do the complete opposite of what was done in Genesis 6:5, that is to keep your mind on God continually as noted in Isaiah 26:3. The imagination comes from the mind and by keeping your mind on God you can only imagine what is good and pleasing to God.


Genesis 6:4 - The inbreeding of angels with humans.

There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
Where Is the Beast? (Part 2) by John W. Ritenbaugh explain how these "men or renown" were called giants because of the influence and that they "were establishing evil, deceitful, violent, and enslaving leadership."

GENESIS 6 – WHO WERE "THE SONS OF GOD"? by Bryan T. Huie examines the theory that these "men of renown" were created by fallen angles that committed fornication with human women. First, Bryan Huie takes a look at all of the Old Testament references to "sons of God" to see if the scripture is referring to angles
Genesis 6:1-4; Deuteronomy 32:8; Job 1:6; 2:1; 38:4-7; Psalm 29:1-2; 89:5-6
The author also makes the connection of the angles mention in Jude 1:6-7 to the "sons of God" mentioned in this scripture.

Genesis 6:3 - Life Span Shortened

And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.
God's Limit on Mans Years by Guy Cramer points out that the 12o years is the limit God placed on man's life. After this declaration was made lifespans began to shorten until it was less than 120 years. Guy Cramer notes that:
some scholars suggest that this 120 years was a prophetic time line until the flood took place. However, we see God's decision was made in Genesis 6:3 after Noah turned 500 in Genesis 5:32. Noah was 600 years old when the flood waters were on the earth. Genesis 7:6 NKJV) Taking these passages we can determine that the flood took place within 100 years after God's decision. So the prophetic interpretation of the Genesis 6:3 is a wrong one.
I agree with Guy Cramer's interpretation. When God makes a declaration it doesn't have to happen immediately. Adam and Eve didn't die immediately after eating the forbidden fruit from off the tree of knowledge.